Putting Genetic Tests to the Test

Putting Genetic Tests to the Test

The Venter study makes several recommendations for direct-to-consumer genetic testing companies. These include a greater focus on the genetic variations that have a high impact on disease risk and a call to use more markers that provide information on risk factors for taking medications, such as the blood-thinner warfarin and cholesterol-lowering statins. (23andme does provide a marker that can indicate a risk of side effects for warfarin.) The researchers also suggest that sites better explain how their markers fit into the overall impact of genes on a disease (for example, whether a given marker represents 5 percent, 20 percent, or 100 percent of the genetic impact on a disease).

Recommendations to the genetics community include conducting clinical studies to validate genetic markers for disease and for behavioral traits in actual patients tracked over time, and giving more attention to non-Caucasian ethnicities.

23andme cofounder Anne Wojcicki and Navigenics cofounder David Agus both agree with the recommendations. “There is a distinct need for transparency and quality in genetic association studies,” says Agus. “We are giving critical information to individuals to help them with their personal health. That information needs to be correct, or we have done a disservice.”

“We plan on working with 23andme to codevelop standards for the field,” Agus adds. This is a voluntary effort that so far has faltered. 23andme science and policy liaison Andro Hsu says there might be a need for a neutral third party that creates standards–he suggested the Centers for Disease Control. Others have talked about the Food and Drug Administration, or even the National Institute of Standards and Technology.

What Venter and company didn’t mention is the word “regulation”–which is likely to happen in some form if the industry is to ensure that information is accurate and consistent. The Nature commentary also doesn’t call for an aggressive and comprehensive effort to validate genetic tests by running studies in the clinic to see which of these markers really do predict disease–a project that may be needed to accelerate the day when these tests become more medically useful for individuals.

Venter does, however, suggest that the latest DNA sequencing technology is rapidly producing a more accurate and thorough alternative to the sort of single DNA markers used by these companies. In just the past few months, the ability of scientists to sequence the entire six billion nucleotides of a person’s genome has become inexpensive enough that it may soon replace the chips currently used by testing companies. Existing tests scan a person’s genome for up to one million markers covering most genetic variations associated with human disease, but they don’t nearly cover them all.

Just two years ago, it cost $1 million to sequence an entire genome; now the price is rapidly dropping to under $50,000, and may be as little as $5,000 by next year.

“Once we have at least 10,000 human genomes and the complete phenotype [disease profiles] with these genomes, we will be able to make correlations that are impossible to do at the present time,” says Venter. “At that stage, genetic testing will be a good investment for private companies and the government.”